Mr Bercow has taken the unusual step of issuing a certificate that effectively exempts material from normal Freedom of Information (FOI) rules.

The move came after a request by the Press Association regarding the tax treatment of a handful of prestigious residences granted to senior figures including the Speaker, Clerk of the House and Serjeant-at-Arms.

The Westminster properties, which are either on the Parliamentary estate or are very close by, are worth many millions of pounds. Living accommodation provided to staff by employers is usually treated as extra income by the taxman.

HM Revenue & Customs considers whether the accommodation is necessary for the job. The taxable benefit can reflect the full rental value, or merely running costs such as utilities - as has happened with the Prime Minister and Downing Street.

Commons documents show that Mr Bercow incurred a taxable benefit of £4,300 for Speaker’s House in 2009/10, with the figure worked out using a “formula based on a percentage of annual taxable salary and period of residence”.

The same year the Clerk of the House's use of 3 Parliament Street was worth £27,000 to him, according to the annual Commons accounts.

However, talks with HMRC resulted in the assessment of the benefit for both Mr Bercow and the Clerk falling to nothing in 2010/11. The accounts stated that “it has been agreed that no benefit in kind liability arose”.

The latest accounts, for 2011/12, again list no taxable benefit for the Clerk, but add that the issue “is currently being discussed with HMRC”.

The change suggests that the tax bill for the Speaker and his senior officials may have been significantly reduced - although the situation is not clear.

The FoI request asked for details of the discussions with HMRC regarding tax treatment of residences. The Commons authorities initially argued that disclosure would inhibit HMRC's ability to enforce “law and order”, and breach data protection rules.

Those objections were later dropped. But Mr Bercow, who ran for office promising greater transparency, maintained that releasing the details would “inhibit the free and frank exchange of views” and “prejudice the effective conduct of public affairs”.

Such section 36 exemptions are usually subject to a public interest test. But in the case of the Commons, the Speaker’s signature on a certificate is taken as conclusive proof that he has reached a “reasonable opinion”.

The Information Commissioner’s office rejected an appeal, confirming that it has no power to challenge Mr Bercow's decision, or examine the evidence on which it was reached.

“The Commissioner is obliged by section 36(7) FOIA to accept the certificate as ‘conclusive evidence’ that the opinion is reasonable in both process and substance and that the alleged inhibition would be likely to occur,” the appeal ruling said.

Last year, the Independent Parliamentary Standards Authority (Ipsa) agreed to disclose similar discussions with HMRC over whether elements of MPs' expenses should be treated as taxable benefits.

The Commons authorities have responded to further questions about the tax arrangements for residences by starting another FoI process.

A spokesman declined to comment on why the initial request had been blocked, insisting the ICO was able to provide “clarification” about its handling.

Maurice Frankel, of the Campaign for Freedom of Information, said: “The Commons is relying on a power of veto which allows it to evade accountability to avoid embarrassment.

“That power shouldn't have been in the Act in the first place. There is already a separate exemption for Parliamentary privilege, to protect the working of Parliament, plus the full range of other FoI exemptions.

“But Parliament insisted on having this right of veto as the price for allowing itself to be covered by FoI at all.

“If disclosure would genuinely harm a legitimate interest, the Commons should argue its case like any other public body and allow it to be tested by the Information Commissioner.”

Matthew Sinclair, Chief Executive of the TaxPayers’Alliance, added: “It’s completely inappropriate for the Speaker to make the final judgement over whether legitimate questions about his own taxpayer-funded perks are of public interest or not.

“His use of this exemption appears to be a blatant attempt to shut down a perfectly reasonable investigation into how taxpayers' resources are being used.

“Given Ipsa’s stance on taxable benefits, the Speaker should not pretend that he is somehow exempt from the same scrutiny which other MPs face over their arrangements, let alone be actively shutting down any such inquiries.”

A Commons spokesman said it had told PA: "The House authorities aren’t commenting save to say that your further request is being dealt with under the terms of the Freedom of Information Act and will follow the normal process."